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  <script>
    var decompressRLElist = function (nums) {
      let res = []
      for (let i = 0; i < nums.length; i += 2) {
        res = res.concat(new Array(nums[i]).fill(nums[i + 1]))
      }
      return res
    };
    console.log(decompressRLElist([1, 2, 3, 4]));
  </script>
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